1. Field of the Disclosure
The described technology relates generally to a fuel cell system with the improved driving performance and a stack thereof.
2. Description of the Related Technology
A polymer electrolyte membrane fuel cell (PEMFC) system uses a polymer electrolyte membrane having a hydrogen ion exchange characteristic to generate electric power and heat. The electric power and heat are generated by an electrochemical reaction selectively transporting oxygen mixed with the air and hydrogen generated by reforming hydrocarbon fuel, such as methanol, natural gas, and the like to the polymer electrolyte membrane. The fuel cell system includes a stack formed by a plurality of unit cells, end plates on the both side of the stacked unit cells, a fuel supply unit, and oxidant supply unit.
The unit cell includes a separator and a membrane electrode assembly (MEA) that forms an anode electrode and a cathode electrode on the both sides of the polymer electrolyte membrane to selectively transport the hydrogen ions. The anode electrode and cathode electrode each include a catalytic layer on the electrolyte membrane, and a gas diffusion layer on the catalytic layer. The separator has a fuel pathway that supplies fuel to the anode electrode by connecting to the fuel supply unit, and the oxidant pathway that supplies oxidant to the cathode electrode by connecting to the oxidant supply unit. In addition, the separator allows the anode electrode and the cathode electrode of neighboring MEAs to be electrically connected in a parallel.
To improve the performance and durability of the stack a uniform supply of fuel, minimum temperature deviation, humidification and improved material movement in the stack are required. In addition, to maintain humidification of the stack and simplify the configuration of the fuel cell system including a balance of plant (BOP), a system for non-humidifying driving of the fuel cell system is required. However, when the existing fuel cell system is driven by a non-humidifying system, a delaminating phenomenon of the catalytic layer appears in a fuel inflow part. In other words, the catalytic layer deteriorates due to the non-humidifying driving, and is physically damaged due to the repetition of the humidifying driving and the non-humidifying driving.